Re: vDSO? (was: [SCM] Web pages branch, master, updated. 357bc0213f1d4049d6ce0c80122987c760c5e506)

[Samuel Thibault]

Thomas Schwinge, le Sun 07 Apr 2013 01:21:51 +0200, a écrit :
> | Having vDSO code might be useful for:
> | 
> |   * `mach_*_self`: `mach_host_self`, `mach_task_self`, `mach_thread_self`?

Mmm, but these are supposed to add a reference count on the send right.

> |   * 
> [[mapped-time_interface|master/microkernel/mach/gnumach/interface/device/time]]
> | 
> |     Every application can then use that via the regular
> |     `gettimeofday`/`clock_gettime` and similar calls instead of using the
> |     special [[hurd/libshouldbeinlibc]]'s `<maptime.h>` interface.
> | 
> |     Can implement [[`clock_gettime` stuff|clock_gettime]] more easily that 
> way,
> |     for example for nanosecond precision?

Oh, I thought gettimeofday was already using the mapped time, but
apparently not. It would definitely be useful to avoid a syscall here.

> |     Now, the [[mapped-time_interface]] is virtualizable -- the question is
> |     whether there is a way so that we can make a compromise here?

I don't see what problem you are seeing here. glibc would mmap
/dev/time, which can be interposed, that's all fine.

Samuel